package org.apache.lucene.search;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Vector;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.MultipleTermPositions;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermPositions;
import org.apache.lucene.search.Query;

/**
 * PhrasePrefixQuery is a generalized version of PhraseQuery, with an added
 * method {@link #add(Term[])}.
 * To use this class, to search for the phrase "Microsoft app*" first use
 * add(Term) on the term "Microsoft", then find all terms that has "app" as
 * prefix using IndexReader.terms(Term), and use PhrasePrefixQuery.add(Term[]
 * terms) to add them to the query.
 *
 * @author Anders Nielsen
 * @version 1.0
 */
@SuppressWarnings("Duplicates")
public class PhrasePrefixQuery extends Query {
  private String field;
  private ArrayList termArrays = new ArrayList();
  private Vector positions = new Vector();

  private int slop = 0;

  /**
   * Sets the phrase slop for this query.
   *
   * @see PhraseQuery#setSlop(int)
   */
  public void setSlop(int s) {
    slop = s;
  }

  /**
   * Sets the phrase slop for this query.
   *
   * @see PhraseQuery#getSlop()
   */
  public int getSlop() {
    return slop;
  }

  /**
   * Add a single term at the next position in the phrase.
   *
   * @see PhraseQuery#add(Term)
   */
  public void add(Term term) {
    add(new Term[]{term});
  }

  /**
   * Add multiple terms at the next position in the phrase.  Any of the terms
   * may match.
   *
   * @see PhraseQuery#add(Term)
   */
  public void add(Term[] terms) {
    int position = 0;
    if (positions.size() > 0)
      position = ((Integer) positions.lastElement()).intValue() + 1;

    add(terms, position);
  }

  /**
   * Allows to specify the relative position of terms within the phrase.
   *
   * @param terms
   * @param position
   * @see PhraseQuery#add(Term, int)
   */
  public void add(Term[] terms, int position) {
    if (termArrays.size() == 0)
      field = terms[0].field();

    for (int i = 0; i < terms.length; i++) {
      if (terms[i].field() != field) {
        throw new IllegalArgumentException(
          "All phrase terms must be in the same field (" + field + "): "
            + terms[i]);
      }
    }

    termArrays.add(terms);
    positions.addElement(new Integer(position));
  }

  /**
   * Returns the relative positions of terms in this phrase.
   */
  public int[] getPositions() {
    int[] result = new int[positions.size()];
    for (int i = 0; i < positions.size(); i++)
      result[i] = ((Integer) positions.elementAt(i)).intValue();
    return result;
  }

  @SuppressWarnings("Duplicates")
  private class PhrasePrefixWeight implements Weight {
    private Searcher searcher;
    private float value;
    private float idf;
    private float queryNorm;
    private float queryWeight;

    public PhrasePrefixWeight(Searcher searcher) {
      this.searcher = searcher;
    }

    public Query getQuery() {
      return PhrasePrefixQuery.this;
    }

    public float getValue() {
      return value;
    }

    public float sumOfSquaredWeights() throws IOException {
      Iterator i = termArrays.iterator();
      while (i.hasNext()) {
        Term[] terms = (Term[]) i.next();
        for (int j = 0; j < terms.length; j++)
          idf += getSimilarity(searcher).idf(terms[j], searcher);
      }

      queryWeight = idf * getBoost();             // compute query weight
      return queryWeight * queryWeight;           // square it
    }

    public void normalize(float queryNorm) {
      this.queryNorm = queryNorm;
      queryWeight *= queryNorm;                   // normalize query weight
      value = queryWeight * idf;                  // idf for document 
    }

    public Scorer scorer(IndexReader reader) throws IOException {
      if (termArrays.size() == 0)                  // optimize zero-term case
        return null;

      TermPositions[] tps = new TermPositions[termArrays.size()];
      for (int i = 0; i < tps.length; i++) {
        Term[] terms = (Term[]) termArrays.get(i);

        TermPositions p;
        if (terms.length > 1)
          p = new MultipleTermPositions(reader, terms);
        else
          p = reader.termPositions(terms[0]);

        if (p == null)
          return null;

        tps[i] = p;
      }

      if (slop == 0)
        return new ExactPhraseScorer(this, tps, getPositions(), getSimilarity(searcher),
          reader.norms(field));
      else
        return new SloppyPhraseScorer(this, tps, getPositions(), getSimilarity(searcher),
          slop, reader.norms(field));
    }

    public Explanation explain(IndexReader reader, int doc)
      throws IOException {
      Explanation result = new Explanation();
      result.setDescription("weight(" + getQuery() + " in " + doc + "), product of:");

      Explanation idfExpl = new Explanation(idf, "idf(" + getQuery() + ")");

      // explain query weight
      Explanation queryExpl = new Explanation();
      queryExpl.setDescription("queryWeight(" + getQuery() + "), product of:");

      Explanation boostExpl = new Explanation(getBoost(), "boost");
      if (getBoost() != 1.0f)
        queryExpl.addDetail(boostExpl);

      queryExpl.addDetail(idfExpl);

      Explanation queryNormExpl = new Explanation(queryNorm, "queryNorm");
      queryExpl.addDetail(queryNormExpl);

      queryExpl.setValue(boostExpl.getValue() *
        idfExpl.getValue() *
        queryNormExpl.getValue());

      result.addDetail(queryExpl);

      // explain field weight
      Explanation fieldExpl = new Explanation();
      fieldExpl.setDescription("fieldWeight(" + getQuery() + " in " + doc +
        "), product of:");

      Explanation tfExpl = scorer(reader).explain(doc);
      fieldExpl.addDetail(tfExpl);
      fieldExpl.addDetail(idfExpl);

      Explanation fieldNormExpl = new Explanation();
      byte[] fieldNorms = reader.norms(field);
      float fieldNorm =
        fieldNorms != null ? Similarity.decodeNorm(fieldNorms[doc]) : 0.0f;
      fieldNormExpl.setValue(fieldNorm);
      fieldNormExpl.setDescription("fieldNorm(field=" + field + ", doc=" + doc + ")");
      fieldExpl.addDetail(fieldNormExpl);

      fieldExpl.setValue(tfExpl.getValue() *
        idfExpl.getValue() *
        fieldNormExpl.getValue());

      result.addDetail(fieldExpl);

      // combine them
      result.setValue(queryExpl.getValue() * fieldExpl.getValue());

      if (queryExpl.getValue() == 1.0f)
        return fieldExpl;

      return result;
    }
  }

  protected Weight createWeight(Searcher searcher) {
    if (termArrays.size() == 1) {                 // optimize one-term case
      Term[] terms = (Term[]) termArrays.get(0);
      BooleanQuery boq = new BooleanQuery();
      for (int i = 0; i < terms.length; i++) {
        boq.add(new TermQuery(terms[i]), false, false);
      }
      boq.setBoost(getBoost());
      return boq.createWeight(searcher);
    }
    return new PhrasePrefixWeight(searcher);
  }

  /**
   * Prints a user-readable version of this query.
   */
  public final String toString(String f) {
    StringBuffer buffer = new StringBuffer();
    if (!field.equals(f)) {
      buffer.append(field);
      buffer.append(":");
    }

    buffer.append("\"");
    Iterator i = termArrays.iterator();
    while (i.hasNext()) {
      Term[] terms = (Term[]) i.next();
      buffer.append(terms[0].text() + (terms.length > 1 ? "*" : ""));
      if (i.hasNext())
        buffer.append(" ");
    }
    buffer.append("\"");

    if (slop != 0) {
      buffer.append("~");
      buffer.append(slop);
    }

    if (getBoost() != 1.0f) {
      buffer.append("^");
      buffer.append(Float.toString(getBoost()));
    }

    return buffer.toString();
  }
}
